#include<iostream>
#include<iomanip>
#include<algorithm>
#include<cmath>
using namespace std;
int m, t, s;
int main()
{
	cin >> m >> t >> s;
	int s1 = m * t;
	if (s1 <= s) {
		cout << 0 << endl;
	}
	else {
		cout << (s1 - s) / t << endl;
	}
	return 0;
}